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Our favorite unheralded Mariners prospects

We shine a light on some players who might be getting overlooked in a suddenly-deep Mariners system

MLB: Seattle Mariners-Media Day
look at this face! herald him!
Jerome Miron-USA TODAY Sports

With all this new talent entering the farm after the draft and a rash of trades, the Mariners’ top prospect list has gotten a gentle shake-up over the past few months. Unfortunately for some of our favorite sleeper prospects, this has pushed them even further down the lists and into the shadows of the system. So we decided to remind you about some possible future Mariners you might have forgotten about or not heard about yet. These are players who fall outside of the big sites’ top prospect lists and for whatever reason—injury, haven’t played stateside yet, undrafted free agent signing/late draft pick, etc.—people seem not to be talking about. Here is their (small) moment in the sun:

Tim: RHP Ty Adcock

This isn’t someone who’s going to turn into Max Scherzer, no, although I hear they’re doing incredible things with genetics nowadays. No, I’m turning to Ty Adcock because have you watched our bullpen this year? It may have stabilized a little but it has been a bit of a roller coaster. To contend, the Mariners will have to find bullpen success inside and outside the organization and Adcock is as likely a candidate as any. Unfortunately he didn’t pitch at all with an injury immediately after being drafted; fortunately, the strange circumstance of the present means he hasn’t really missed development time compared to his draft class other than George Kirby. At his best, Adcock may well touch triple digits with the heater, showing off a hammer of a slider to match that should play well in a single-inning role. The Mariners liked him enough to burn an 8th-rounder on him and there’s a lot to dream on here: a former catcher, Adcock is relatively new to the mound, so the hope is that he can quickly harness his newfound mound talents.

Connor: RHP Devin Sweet

Just barely cracking Seattle’s Top 30 prospect list at #30 on FanGraphs, Devin Sweet was a revelation last summer. Joining the org as an undrafted free agent out of North Carolina Central University in 2018, he’s done nothing but perform in the lower minors, putting up a career K/BB ratio of over 5-to-1. After entering West Virginia’s rotation last June, he went on an exceptional run, including a stretch where he struck out 45 hitters while walking just one across five starts. He earned a late promotion to Modesto, and continued to shine, giving up just a trio of runs over a trio of starts to go with a FIP of 2.75 and nearly seven strikeouts to every walk.


Sweet is a little undersized for a starting pitcher at 5’11” and 183 pounds, and his fastball velocity at 91-93 is decent - although not overpowering - and represents a significant jump from his 2018 velo, which sat closer to 86-88 [Gas Camp, baby! -Ed.]. His true strength is a changeup with great late movement, and as is, it’s likely already a big league pitch. He’s also shown a willingness to throw it in nearly any count, whether it’s a complement to the fastball or leading with it to pitch backwards. Sweet’s success as a starter going forward will depend on the development of his slider, but even if that third pitch never grows, he stands a decent chance at cracking the bigs as a multi-inning reliever given the advanced changeup and ever-improving fastball.

Joe: C German Guilarte

Alright, I’m reaching down the well a bit, I know. The Mariners are an organization that currently lack catching talent with upside but I think Guilarte has quite a bit. Admittedly, I’m a sucker for international catchers. I was a big fan of Danny Santos in the 2016 class and I’m a big fan of Guilarte here. This Venezuelan backstop signed with Seattle for $200,000 last July, a sizable investment. Guilarte, 17, is a 6-foot-2, 190 pound prospect with juice in the bat and impressive chops behind the plate. In showcase events, his pop times were regularly 1.95-2.10, already grading out as an average big league throw-and-catch guy. In the box, Guilarte produces some impressive BP with a slightly wide stance, a medium stride, sticking in his back hip before separation at the point of contact. It remains to be seen what the hit tool is going to look like here, but at worst I think the Mariners have a catcher with average power and an average arm. There’s still some work to do behind the plate as his framing needs work and the glove drifts a bit upon reception. Guilarte is reasonably quick out of the box and is light on his feet, suggesting there may be some athleticism to his game on the basepaths. Again, all this at just 17-years-old. Suppose the power and arm tick up just half a grade between now and his potential arrival in 2025? You’re talking about a 55 power, 55 arm and potential 45 runner behind the plate. That’ll absolutely play at the big league level.

John: LHP Brayan Perez

There was a time when Perez, by dint of having a pitching arm, two pitching legs, and a Mariners hat, was among the system’s Top-30 prospects. The rebuild has added many players ahead of him, but Perez remains worth keeping an eye on. He’s a soft tossing lefty with a funky short-arm load that he repeats well despite an unbalanced motion with his front side. His crossfire delivery seems to add deception, as he’s worked a fastball, breaking ball, changeup combo to success through Everett despite his youth for the level. This year, living in Arizona full-time, Perez is missing his first shot at full season ball, in a system that literally may not have enough spots for SP prospects to fit him in if they go ahead with minor league contraction.

Guys with Perez’s stuff often get scraped away by better competition, but his plus command, decent off-speed combo are the tools Seattle has preferred, then looking to add velo after the fact like a daring culinary creative dashing spices on post-grill. Perez’s best bet may be a long relief/Vidal Nuño role, but his off-speed can play if his heat ticks up. Don’t count on it, but don’t count him out.

Kate: SS Juan Querecuto

I was going to pick RHP Jarod Bayless for this (listen to the podcast episode with him if you haven’t, you will learn so much about pitching in an entertaining way!), but I wanted to remind you all that Juan Querecuto...exists? It’s weird to call a guy who signed in 2017 for $1.2M “unheralded” and certainly there are times when Querecuto has gotten his shine, but he’s since fallen off all the top prospect lists—FanGraphs didn’t even include him in their top 38 this spring. Also, I polled the staff to see if it was cheating for me to name Querecuto as an unheralded prospect and got a fair number of “who?” responses. Querecuto suffered a torn meniscus early in 2019 that required surgical repair and got a slow start to his season, and maybe wasn’t 100% back as he struggled in the AZL, striking out a ton (37.6%), swiping just two bases, and overall waving a soggy baguette at the plate in just under 100 plate appearances. Querecuto has always been a glove-first shortstop and the bat was the question, and unfortunately he’s now losing out on a year of development (his Instagram stories show him working out in his home, mostly, still wearing a brace on that right knee). But Querecuto has strong baseball bloodlines, a plus glove, gorgeous athleticism in his 6’2” frame, and an advanced understanding of the game, and he’s still just 19 years old. I’m not ready to write him off yet.

Amanda: RHP Jack Anderson

You might remember Anderson from videos posted this February, where he showed off his submarine delivery for the beat writers to film and tweet. (Also, remember February? What innocent fools we were.) This spring was his first invite to the big league camp, and his unorthodox delivery garnered some attention. It may flumox some hitters, but delivery aside he’s not a flashy pitcher. His fastball and slider will strike out a good number of batters, but his real strength lies in keeping the ball down. He induces ground balls over 60% of the time and in 200 minor league innings, has only allowed one home run.

Although Anderson hasn’t been granted high prospect rankings, he was expected to make his major league debut sometime this year. Unfortunately, that’s unlikely to happen because he has not been picked to spend any time at the alternate site this year. Still, the submariner is likely to emerge as a Mariner in the near future. The 2016 23rd round draft pick out of Penn State has put up good minor league numbers (2.20 ERA, 1.25 WHIP, 2.65 BB/9, 9.03 SP/9), making him almost certain to get a shot soon. In the meantime, he’s been running a fundraiser for Young, Black & Lit, which helps provide diverse children’s books to schools in the Chicago area, that’s worth checking out: